1. Field of the Invention
The present invention relates to a process for making a connection between superconductive wires and to a connection obtained by this process.
2. Description of Background Information
When a superconductive circuit whose principal characteristic is that of having a zero electrical resistance, is made, linkages between superconductive wires must be made, either to obtain sufficient lengths or for experimental needs. Now, this contact between the superconductive wires which are constituted in a conventional manner by a metallic matrix, for example of bronze or copper, enclosing at least one superconductive strand or filament (made of alloys or mixtures of metals such as niobium titanium or niobium-tin), introduces an appreciable electrical resistance in the circuit and consequently reduces the advantages of the superconductive wires.
In an attempt to obtain a very low contact resistance between superconductive wires, it has already been envisaged to weld these wires by subjecting the strands or filaments of this wire to ionic bombardment in order to clean them, then by spraying an additional material extracted from a target likewise subjected to ionic bombardment, which furnishes welding layer connecting the two wires. Such a process is described in French Pat. No. 2,397,720 which issued from application No. 77 21671 filed July 13, 1977.
Such a process presents the drawback that the residual contact resistance established between the two welded wires is still relatively high, of the order of 10-8 ohm. Such a high resistance consequently limits the use of superconductive coil in permanent mode. Another drawback of the above process is that, to carry it out, it requires a complex and expensive installation for ionic bombardment.
Another known process, such as described in British Pat. No. 1 298 068, consists in "cold welding" the wires by exerting thereon a high pressure by mechanical means or by an explosion. Such a process presents the drawbacks of requiring the use of means which are inconvenient and of not enabling a very low residual contact resistance to be obtained.